Intervention, causal reasoning, and the neurobiology of mental disorders: Pharmacological drugs as experimental instruments

The prospects of precision psychiatry

Since the turn of the twenty-first century, biomedical psychiatry around the globe has embraced the so-called precision medicine paradigm, a model for medical research that uses innovative techniques for data collection and analysis to reevaluate traditional theories of disease. The goal of precision medicine is to improve diagnostics by restratifying the patient population on the basis of a deeper understanding of disease processes. This paper argues that precision is ill-fitting for psychiatry for two reasons. First, in psychiatry, unlike in fields like oncology, precision medicine has been understood as an attempt to improve medicine by casting out, rather than merely revising, traditional taxonomic tools. Second, in psychiatry the term "biomarker" is often used in reference to signs or symptoms that allow patients to be classified and then matched with treatments; however, in oncology "biomarker" usually refers to a disease mechanism that is useful not only for diagnostics, but also for discovering causal pathways that drug therapies can target. Given these differences between how the precision medicine paradigm operates in psychiatry and in other medical fields like oncology, while precision psychiatry may offer successful rhetoric, it is not a promising paradigm.

Dopamine manipulations modulate paranoid social inferences in healthy people

Altered dopamine transmission is thought to influence the formation of persecutory delusions. However, despite extensive evidence from clinical studies there is little experimental evidence on how modulating the dopamine system changes social attributions related to paranoia, and the salience of beliefs more generally. Twenty seven healthy male participants received 150mg L-DOPA, 3 mg haloperidol, or placebo in a double-blind, randomised, placebo-controlled study, over three within-subject sessions. Participants completed a multi-round Dictator Game modified to measure social attributions, and a measure of belief salience spanning themes of politics, religion, science, morality, and the paranormal. We preregistered predictions that altering dopamine function would affect (i) attributions of harmful intent and (ii) salience of paranormal beliefs. As predicted, haloperidol reduced attributions of harmful intent across all conditions compared to placebo. L-DOPA reduced attributions of harmful intent in fair conditions compared to placebo. Unexpectedly, haloperidol increased attributions of self-interest about opponents' decisions. There was no change in belief salience within any theme. These results could not be explained by scepticism or subjective mood. Our findings demonstrate the selective involvement of dopamine in social inferences related to paranoia in healthy individuals.

Informing materials: drugs as tools for exploring cancer mechanisms and pathways

This paper builds on previous work that investigated anticancer drugs as 'informed materials', i.e., substances that undergo an informational enrichment that situates them in a dense relational web of qualifications and measurements generated by clinical experiments and clinical trials. The paper analyzes the recent transformation of anticancer drugs from 'informed' to 'informing material'. Briefly put: in the post-genomic era, anti-cancer drugs have become instruments for the production of new biological, pathological, and therapeutic insights into the underlying etiology and evolution of cancer. Genomic platforms characterize individual patients' tumors based on their mutational landscapes. As part of this new approach, drugs targeting specific mutations transcend informational enrichment to become tools for informing (and destabilizing) their targets, while also problematizing the very notion of a 'target'. In other words, they have become tools for the exploration of cancer pathways and mechanisms. While several studies in the philosophy and history of biomedicine have called attention to the heuristic relevance and experimental use of drugs, few have investigated concrete instances of this role of drugs in clinical research.

Natural kinds, psychiatric classification and the history of the DSM

This paper addresses philosophical issues concerning whether mental disorders are natural kinds and how the DSM should classify mental disorders. I argue that some mental disorders (e.g. schizophrenia, depression) are natural kinds in the sense that they are natural classes constituted by a set of stable biological mechanisms. I subsequently argue that a theoretical and causal approach to classification would provide a method for classifying natural kinds that is superior to the purely descriptive approach adopted by the DSM since DSM-III My argument suggests that the DSM should classify natural kinds in order to provide predictively useful (i.e. projectable) diagnostic categories and that a causal approach to classification would provide a more promising method for formulating valid diagnostic categories.

Depression and suicide are natural kinds: implications for physician-assisted suicide

In this article, I argue that depression and suicide are natural kinds insofar as they are classes of abnormal behavior underwritten by sets of stable biological mechanisms. In particular, depression and suicide are neurobiological kinds characterized by disturbances in serotonin functioning that affect various brain areas (i.e., the amygdala, anterior cingulate, prefrontal cortex, and hippocampus). The significance of this argument is that the natural (biological) basis of depression and suicide allows for reliable projectable inferences (i.e., predictions) to be made about individual members of a kind. In the context of assisted suicide, inferences about the decision-making capacity of depressed individuals seeking physician-assisted suicide are of special interest. I examine evidence that depression can hamper the decision-making capacity of individuals seeking assisted suicide and discuss some implications.